The 42-year-old construction materials salesman has just been released from Hanoi's Hospital for Tropical Diseases, where both he and his older brother were patients.

Hung is now back at home with his wife and children. But his brother Nguyen Hung Viet died from his illness.

Hung still does not know how they both contracted H5N1, the often deadly virus that causes the respiratory illness bird flu.

"I guess we both got it from the last meal we shared together," Hung said.

"I'd just got back to Thai Binh, where I'm originally from, to visit my brothers. They threw a welcoming dinner where we had our favourite dish, 'tiet canh', which is made with chopped congealed raw duck blood and herbs.

"The duck was plump and looking healthy, so we didn't have the slightest suspicion that it might be sick. Moreover, we were thinking chicken flu only exists in the south of the country," he said.

Just one day after the meal, Hung's eldest brother fell sick with a temperature.

But the family waited a whole week before they finally took him to hospital.

H5N1 BIRD FLU VIRUS

Principally an avian disease, first seen in humans in Hong Kong, 1997

Almost all human cases thought to be contracted from birds

Isolated cases of human-to-human transmission in Hong Kong and Vietnam, but none confirmed

"It was New Year's Day. The hospital was running on minimal staffing and only got back to normal operating schedule three days afterwards. It was an unfortunate timing for him.

"At that point, my brother was already too weak. He couldn't breathe, his left lung was totally damaged.

"Yet the doctors didn't think he had bird flu, and his tests came back negative. So I didn't take any preventive measures while taking care of him. I spent days and nights next to his sick-bed, yet I didn't even bother with a mask," Hung said.

Hung's brother died on 10 January. Later on the same day, Hung developed a bad fever.

"I got really worried so the next day I went to a clinic where they took a scan of my lungs. The result came back not so good, and when I complained about difficulties in breathing they referred me to the same hospital where my brother was treated.

"In a way I was lucky that at that time, a number of people had died in the south of bird flu and the media was raising the alarm about this matter.

Panic

"I was immediately put into quarantine. My concern grew each day, as my temperature was staying extremely high. At the worst moment, two thirds of one lung was severely affected.

My temperature was staying extremely high. At the worst moment, two thirds of one lung was severely affected

Nguyen Thanh Hung

"Still, when the doctors told me I had bird flu I was totally shocked. I knew nothing about it and it scared me. The test on the specimen taken from my brother also came back that day, as positive.

"I got into such a panic, even though my fever was beginning to subside. For two nights, I didn't sleep.

"I told myself I should not doze off at any point - something may happen inside me, inside my brain, and I may never wake up.

"Only when my fever had gone and the doctors told me my lungs had made a miraculous recovery did I feel a little relieved," Hung said.

Hung has since fully recovered and was finally released from the hospital on 28 January.

But the doctors are still investigating his case.

Their biggest fear is that Hung contracted the virus from his brother while looking after him at the hospital.

If that were the case, it would be the second suspected human-to-human transmission of bird flu in Vietnam.

Scientists are deeply concerned about the ability of the flu virus to combine with a human form and transmit easily from human to human. If this happened, the world could face a pandemic of devastating scale, experts have warned.

I now know everything about preventing bird flu, I should be employed by the Health Ministry to do their awareness campaign

Nguyen Thanh Hung

Now back to his normal life, Hung has decided to take a long leave of absence from his work.

"They were only too happy to release me. Not everybody believes that I don't have the virus anymore and that it is not easy to contract bird flu virus.

"It is like having a stigma, some people look at you with suspicion and fear. So I think it's best to avoid having too much contact with other people.

"I also look out for any slightest symptoms of bird flu in my family. I'm watching like a hawk," he said.

When it comes to his food, Hung admits he no longer eats those "tricky delicacies" he used to love.

"We have also stopped eating chicken, duck, and poultry in general. Maybe it is too cautious but we cannot risk our health.

"We have to stay alert, very alert," Hung said, adding with a chuckle: "I now know everything about preventing bird flu. I should be employed by the Health Ministry to do their awareness campaign".